In the 2006-07 academic year, 4,540 academic staff arrived from overseas to start work in UK universities. At the same time, only 1,325 staff left UK institutions to go abroad. The figures, from the Higher Education Statistics Agency, question whatever happened to the "brain drain".

This was a term coined in the late 1950s and promoted in the following decade by the Royal Society, which had become concerned by the loss of a number of top scientists to overseas institutions. It re-emerged in the 1990s when higher education in the UK was experiencing funding cuts and low morale. But with nearly 20% of UK academic staff now non-UK nationals, the concept seems distinctly old hat.

No threat from the US

In fact, the Global Talent Index Survey, carried out at the end of last year by the consulting firm Heidrick and Struggles and the Economist Intelligence Unit, warned that the US - once feared as the chief stealer of British brains - was facing increasing competition from the UK when it came to importing talent. It suggested that this was partly due to UK government efforts to attract skilled immigration, such as through the Highly Skilled Migrant Programme. Tougher immigration rules in the US post-9/11 have also been a factor.

Universities UK (UUK), which carried out research last year on the international market for academic staff, says the good reputation of UK universities has also played its part.

"Obviously, we are seen as an attractive place to come to work," says Diana Warwick, chief executive of UUK. "We have a lot of institutional autonomy and academic freedom." In addition, the UK benefits from strong links to the rest of Europe, the US and the Commonwealth, so that overseas academics coming here to work are more likely to feel at home, she says. As the number of international students studying in the UK has increased, particularly the number on doctoral programmes, so has the number choosing to stay on in the country and pursue an academic career. "Also, we are good at research. If you are a successful researcher, this is a good place to come."

Susan Robertson, professor of the sociology of education at the University of Bristol, who is conducting research on the globalisation of higher education, suggests that brain-drain fears have also receded because global mobility is viewed more positively now. It is considered a good thing for academics to experience academic life in other countries, and all the evidence shows that most UK academics who go abroad do return later. As a result, these days the buzz term is "brain circulation". This does not mean UK universities are entirely relaxed about their academics' movements. While overall more academics come into the country than leave it, the large numbers coming in are at lecturer, researcher and other grades. At senior lecturer/researcher and professorial levels, more academics are leaving.

A study by the Higher Education Policy Institute carried out in 2005 suggested there wasn't too much to worry about because, while the UK lost more staff with publications to their name than it gained, when it came to highly cited researchers, it gained more than it lost. "Although there may be a net quantitative loss to the UK," it concluded, "there is a qualitative gain."

It nevertheless remains something that UUK is keen to monitor, particularly because competition is intensifying most at senior levels. This is due in part to the proliferation of global league tables of universities, most of which include a category relating to numbers of senior-level staff and publications.

Then, there's the greater emphasis in the UK and elsewhere on the "knowledge economy" - the feeling that universities have become an increasingly vital part of their nation's economic wellbeing and therefore need to attract and keep hold of as many top brains as they can get.

In addition, there are a growing number of players in the higher education market. Large developing economies such as China and India are investing significant amounts in their higher education systems, but so are smaller economies, such as Singapore and Malaysia. As a result, all these countries are likely to retain more academic staff than they used to, and to attract back any that spend time overseas.

Development of the European Higher Education Area by 2010 is also likely to increase demand for academic manpower. The international recruitment market in higher education is a fluid one. Between 2003-04 and 2005-06, the number of academic staff from China, Japan and east Asia working in the UK grew by nearly a third, and by nearly as much from eastern and central Europe. It could drop just as quickly.

Science competition

Competition remains particularly intense in the sciences, from which UK universities appoint most of their international recruits. Not surprisingly, the highest proportion of foreign staff working in the UK are language specialists. Mathematical sciences, computer science and engineering come next. In many of these areas, international staff are taking jobs that institutions would struggle to fill by relying on recruits from the UK. They are also the areas most prized in the "knowledge economy". This is something that worries UUK, which warned in its report of over-reliance on non-UK staff because they could easily choose to return home or go elsewhere.

UUK is also concerned about the possible impact of new immigration rules, due to be introduced this autumn, which mean that visiting academic staff would need sponsorship from third parties outside the university. The fear is that by discouraging visiting researchers, the new rules could have a knock-on effect on international recruitment as a whole. Academic staff could also be hit by government proposals to tax non-domiciles.

Nevertheless, Robertson is confident that the UK is likely to continue to attract high numbers of international staff as the academic world continues to become more globalised. And she has also identified a trend that suggests the loss of a few brains to other countries may not be as draining as it seems. New Zealand and Scotland have both introduced schemes designed to tap into the knowledge and experience of academic nationals who have gone overseas and encourage them to feed back what they have learned for the benefit of their mother country. "It's an interesting twist on the idea of the academic abroad," she says.